Blended lubricating oils



Patented Jan. 15, 1946 BLENDED LUBRICATING OILS David w. Young and Theodore J. Peters, In,

Roselle, N. J... assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application July 15, 1942, Serial No. 451,060

Claims. (Cl. 252-42.?)

This invention relates to a method of inhibiting metal Staining tendencies in materials containing free sulfur or sulfur compounds containing loosely combined sulfur.

Many materials, particularly liquid petroleum products of various kinds, such as motor fuels, burning oils, lubricating oils, etc., contain naturally occurring free sulfur or sulfur compounds having sulfur in loosely combined form. or contain various additives in which a certain amount of sulfur of this form occurs, and such materials have a tendency to form stains on metal surfaces with which they come into contact, particularly when the metal is copper or a copper alloy. In the case Of copper-containing metals the stain consists of a copper sulfide and is brassy to red, blue or black in color, depending on the intensity of the corrosive action. This stain is not onl unsightl but, if allowed to accumulate, it may chip off and clog up narrow conveying lines. Itis an object of the present invention to provide a simple method of inhibiting this staining tendency by chemical means.

In accordance with the present invention the materials containing sulfur-yielding impurities are simply treated with a small quantity of an alkali or alkaline earth metal cyanide or an organic cyanide, generally termed a nitrile. Methods of applying this process to the treatment Of specific types of materials, such as lubricating oils and motor fuels, will be discussed in detail below, although the process has wide application and may be used for treating any materials containing the objectionable metal staining sulfur impurities.

The invention has particular usefulness in the treatment of lubricating oils that are blended with additives or the organic sulfide type which sometimes contain considerable amounts of free or loosely combined sulfur, for example, the monosulfides or polysulfides ofalkylated phenols,

- e. g., the monosulflde of tertiary amyl phenol,

the monosulflde or isooctyl phenol, and the vari- Ous metallic salts of such compounds; These additives have been found to be quite satisfactory for inhibiting oxidation and preventing undue ,corrosion of alloy bearings, sludge formation,

such ditives tend to stainthe surfaces of metal 6'' tanks, conveying lines, etc., which are composed of copper or copper-containing alloys; Such copper-corrosive oils are also objectionable in that they maybe active enough to cause pitting of such engine parts as copper or brass bushings so that their replacement becomes necessary. Methods heretofore proposed for removing the metal staining tendency include heating the additive in oil at high temperatures, also treatin with active carbon in oil solution and filtering. These methods are only partly effective or are very costly.

In accordance with the present invention the tendency of a sulfur-containing additive to impart staining characteristics to mineral lubricating oils is very effectively reduced by treating the additive with a small percentage of an alkyl or aryl cyanide or with a metal cyanide. The most desirable aliphatic cyanides are the alkyl cyanides or nitriles having more than four carbon atoms and preferably from 10 to 20 carbon atoms, for example, lauronitrile, undeco nitrile, margaronitrile, stearonitrile, sebacic dinitrile, and nitriles corresponding to the fatty acids obtained from cocoanut oil. Alkyl nitriles having less than ten but more than founcarbon atoms may also be used to advantage, typical examples of these being capronitrile (amyl cyanide), valeronitrile (butyl cyanide), oenanthonitrile (hexyl cyanide), and the like. It may be mentioned that high molecular weight aliphatic nitriles are generally non-toxic in character. Among the aromatic cyanides may be mentioned phenyl cyanide and in general any aromatic oil-soluble cyanide.

As regards metallic cyanides, those of sodium, potassium, lithium, calcium, barium, and strontium are satisfactory. Cyanides of metals other than the alkali or alkaline earth metals are generally not desirable because of lack of requisite solubility in water, mineral oil or other mutual solvents. However, if a sumciently high proportion of metal cyanide is used, some improvement can be eflected by contacting the sulfur-containing material directly with the cyanide without the aid of a solvent. This procedure would permit the use of such cyanides as those of zinc, cobalt and nickel, if desired. Nevertheless, sodium, potassium or calcium cyanides will normally be chosen because of availability, relatively low cost and good solubility.

,It is usually desirable to treat the sulfur-containing'additive with the cyanide in the presence of a material which has at least a small tend ency to act as a mutual solvent. In the case of organic nitriles the lubricating oil often used as a means of preparing concentrates of the additive will act as the common solvent. When the metal cyanides are used, water may serve as the propyl alcohol, may be added to furnish a common solvent. Even with the alkali cyanides, however, an improvement may be obtained without other solvent by adding a sumcient amount of the cyanide directly to'the oil containing the additive.

An additional advantage to be obtained when using the nitriles is that they may serve to partly or completely replace such auxiliary agents as the higher alcohols, e. g., stearyl alcohol, which are often employed in metallic detergent compounded lubricants of this type to avoid foaming during preparation and to assist the metallic additive in dispersing sludge when the finished. oil is employed as an engine lubricant.

The exact nature of the effect of the addition of the cyanide is not fully understood, but it is believed that the basic reaction involves the for-\ mation of a sulfocyanate, according to the followingequation a the additional sulfur atoms quite loosely, and the longer the sulfur chain the more loosely the sulfur is held. As an illustration, it is believed that the barium salt of isooctyl phenol polysulfide has the following formula .The monosulfide is produced by reacting isooctyl phenol with sulfur dichloride, while the disulfide is produced by the reaction with sulfur monochloride. An additive which-imparts to lubricants good detergency and sludge dispersive properties and low corrosive tendencies toward alloy hearings in heavy duty operation of gasoline and Diesel engines can be prepared by making the barium salt of a mixture of the monosulfide and disulflde. It is possible that in preparing this material a small proportion of polysulfide is also formed. Although in commercial production such an additive is usually satisfactorily nonstaining toward copper, certain batches will be found which do stain copper excessively and are undesirable from this standpoint. There is apparently no really satisfactory explanation for this behavior, but it may be due to the instability of the sulfurmonochloride used in the preparation. Whether or not the sulfur which causes the staining tendency is free sulfur introduced by means of impure sulfur halide or whether'it is produced by the splitting off of sulfur from the sulfur chain in the polysulfides, a certain amount of free or loosely combined sulfur is often present in commercially produced compounds of the above described type, and it is believed that this free or active" sulfur reacts with the cyanide to produce a sulfocyanate, while the remaining sulfide product is correspondingly freed from unstable sulfur.

It has been found that the. above described reaction takes place in alkaline as well as acid media. Hence, the method can be used for the treatment of metal soaps as well as alkaline salts of phenol sulfides and the like. The reaction appears to be unique as a reducing reaction which can be conducted in an alkaline medium.

If in carrying out the method of the present invention a non-aqueous inert solvent is used, such as a low molecular weight alcohol, the solvent is removed by distillation after the reaction, and if the organic or inorganic sulfocyanate is not oil-soluble, the latter is removed by filtration.

The organic compounds which are useful as lubricating oil additives and which at the same time often tend to yield sulfur to an extent sufficient to cause undesirable staining of metal surfaces, and whose staining tendencies can be eliminated or greatly minimized by the method of the present invention, include all types of additives which contain loosely combined sulfur in the molecule or which by their method of manufacture are associated with free sulfur or with compounds containing loosely combined sulfur. These include compounds of the mercaptanor organic sulfide type, particularly the latter. The organicsulfides have at least one sulfur atom combined with two aliphatic radicals, two aromatic radicals, or one aliphatic and one aromatic radical. The invention includes especially the treatment of lubricating oils containing sulfides or polysulfides of alkylated phenols and their metallic salts. Other types of materials'include the sulfides of olefins, e. g., diisobutenyl disulfide, also sulfurized isobutylene polymer oil, sulfurized terpenes, sulfurized unsaturated alcohols, sulfurized oleic acid, sulfurized cracked paraffin wax, and other sulfurized olefinic materials.

A satisfactory measure of the staining tendency of a lubricating oil containing sulfide type additives can be made using a modification of the conventional A. S. T. M. corrosion test (Test D130-30), known as the copper strip test, the

modifications involving the employment of both one-half hour and three hour test periods at a temperature of 212 F. If the strip is not stained or if only a light brassy stain is shown, the oil is considered-satisfactory. Oils which produce a definitely brassy, red, red-brown, blue, or black stain are generally considered not satisfactory.

As to the quantities of the organic nitriles or metal cyanides which are required for inhibiting the staining effect of sulfur-containing additives,

it is generally desirable to add from 2% to 10% of the nitrile, based on the weight of the additive present in the oil. When using metal cyanides, quantities from 2% to 5%, on the same basis, are

generally sufficient, although amounts up to 10% may sometimes be employed.

In the following examples are shown actual tests made on lubricating oils containing various additives, with and without the addition of the cyanides. These examples are not to be considered as limiting the scope of the invention in any manner.

EXAMPLE 1 aaeasis ing point -135 C. and 70%-75% aromatic content) were placed in a suitable reaction vessel and refluxed for one hour to remove traces of water. The temperature was reduced to C. and-9.3.7 mls. of sulfur. dichloride were added slowly. withslight agitation, the temperature being permitted to rise to 30 -35 C. 45 mls. of sulfur monochloride were then slowly added at the same temperature. After standing overnight steel rod which was then immersed in the oil and rotated at 600 R. P. M., thus providing sumcieut agitation of the sample during the test. Air was then blown through the oil at the rate of 2 cu. ft. per hour. At the end of 16 hours the hearings were cleaned and weighed. The weight loss of the hearings used is the measure of the corrosiveness of the oil.

The following table shows the results 01 the tests with the oil blends described above as well as with a sample of the oil base used in preparing at room temperature the sulfurized product was the blends.

. Table 1 Comm strip test 1 0 Corrosion test I hour 3 hours Mill 1m Base 0 N0 stain Ve light stain "Ti... Base oil additive Red ate Da red-brown stain. 36 Base 011 +NaCN-treated additive (2% treat) Ligtlgtn brassy Light brassy stain... 29 Base oil-i-NaCN-treated additive (5% treat) No stain Slight staln- 22 an anti-foaming agent, and 30.5 grams of hydrated barium hydroxide (BMQH) 2.81120) were added gradually, holding the temperature at 105 to 110 C. The product was then heated for a short period at 130 C.

Another portion of the oil solution of sulfurized isooctyl phenol (125.8 grams) was blended with 6.5 grams of stearyl alcohol and the barium hydroxide added in two portions. The first portion (23.? grams) was added as before, holding the temperature at 105 to 110 C. At this point, while water of reaction was present, 2.6 grams of commercially pure sodium cyanide were added, then the remaining 7.2 grams of barium hydroxide were added and the product heated for a short period at 130 C. To remove insoluble materials formed by the reaction with sodium cyanide the product was treated with 3% of a filter aid and filtered through paper under vacuum. The amount of sodium cyanide added in this procedure was equivalent to 2% based on the barium salt in the finished product. which contained 4.0% of the salt.

A third preparation was made in the same manner, except that 5% of sodium cyanide was used.

Each of the products was blended to a concentration of 2.5 weight per cent in a solvent extracted mineral lubricating oil of 52 Saybolt seconds viscosity at 210 F. and submitted to standard copper strip tests (described above) conducted for one-half hour and for three hours. The blends were also submitted to a bearing corrosion test conducted as follows:

500 cc. of the oil were placed in a glass oxida-' tion tube (13""- long and 2%" diameter), fitted at the bottom with a A" bore inlet tube perforated to facilitate air distribution. The oxidation tube was then immersed in a heating bath so that the oil temperature was maintained at 325 F. during the test. Two quarter sections of automotive bearings of copper-lead alloy of known weight, having a total area of sq. cm. were attached to opite sides of a stainless The bearing corrosion tests demonstrate that the corrosion inhibiting action of the additive was not impaired by the cyanide treatment, but, if anything, was slightly improved.

Era 2 In a further series of tests various alkyl' nitrlles (RCN) were added to oils containing both isoof isooctyl phenol disulfide and 61.80 grams of the'base oil used in Example 1. From 2 to 10 grams of RCN were added in each case, followed by the addition of 34.2 grams of barium hydroxide (Ba(OH)2.8I-Is0), and heating for a short period to 0., except in the case of the portion treated with lauronltrile, when the blend was heated to C. The products were then treated with 3% of a filter aid and filtered through paper under vacuum. All of the products were blended in a highly extracted mineral lubricating oil of 52 seconds Saybolt viscosity at 210 F. to form a solution of 2.5% concentration by weight and submitted to the one-half'hour copper strip test and to the 16 hour corrosion test described in Example 1. For comparison a similar test was made in which 10 grams of stearyl alcohol were added in place of the RCN. The results are as follows: i

Y mural I Copper strip tests were applied to a series of lubricating oil blends containing various salts of tertiary amyl phenol sulfide, as well as to a blend containing diisobutenyl disulflde. These blends were prepared by. first making a solution of the additive in isopropyl alcohol, adding 5% of sodium cyanide, based on the weight of additive used, then heating to near the boiling point of m the alcohol and adding a sufllcient amount of a highly extracted mineral oil of 53 seconds Saybolt viscosity at 210 I to form aEcIear solution. The mixture was then heated for-about 12 minutes and filtered through paper, and the solvent stripped off under vacuum. The one-half hour 15 copper strip test was then applied to the solutions formed in this mannerras well as to oil blends prepared simply by dissolving the additive in the oil, using no cyanide or alcohol. In

each case the strength of the blend was adjusted so that each 100 ms. of oil contained 2% grams The diisobutenyl sulfide employed in the above tests was prepared by reacting diisobutylene' with sulfur monochloride in the presence of sodium carbonate and further reacting the product thus formed with isopropyl alcohol saturated with ammonia.

The present invention may advantageously be applied to the treatment of various other liquid petroleum products, such as gasolines, kerosenes, Diesel fuels, heating oils, etc., which frequently contain certain amounts of corrosive sulfur.

In the case of gasolines there may be present a certain amount of free sulfur which-has the metal staining tendency described above. Furthermore, some refiners resort to some process 85 for the conversion of mercaptans, occurring in crude gasolines, to unoifensive alkyl disulfldes, the most common of such sweetening processes being the widely known doctor treatment,

consisting in the treatment of the fuel with sulso fur and sodium plumbite in caustic soda. The

mercaptans are converted into alkyl disulfides which remain in the gasoline, while the lead is precipitated as lead sulfide. This process calls for the use of an excess of sulfur over that theoas retically required in order to accelerate the precipitation of the lead sulfide. This excess of sulfur remains, at least in part. in the sweetened product, so that the same may become corrosive.

Also, the disulfldes formed are sometimes objec- 10 tionable for the same reason. g

It has been found that the free sulfur and the sulfur yielded by the disulfldes can be removed from the products by treating the same with a arcane f or by adding an organic nitrilc, Preferably one having a molecular weight above about 83, directly to the gasoline or naphtha and heating the mixture. In either case the sulfur is converted into a sulfocyanate form and may be removed from the gasoline by distillation.

In the case of Diesel fuels, sulfur-yielding compounds may be present because of the addition of ignition promoters, such as nitrogengtetrasulfide, which. on standing yields considerable quantities of free sulfur. v

The method has application also to the purlflcation or color improvement of sulfur-containing reagents themselves, for example, sulfur monochloride, which is somewhat unstable and tends to yield free sulfur on standing, causing the product to acquire ared or even black color. Treatment of such material with a small percentage of a cyanide, e. g., from 0.02% to 2.0% of sodium cyanide, results in clearing up the color of this product thus making it a more attractive product from the marketing standpoint. Also, when cyanide treated sulfur halides are employed to produce sulfur-containing additives for lubricants, such additives are more likely to be non-staining to copper than are corresponding 'materials prepared with untreated sulfur halides.

The present invention is not to be considered as limited in any way by the various examples described herein, which are given by way of iilustration only, nor by any theory as to the operation of the invention, but is to be limited in scope solely by the terms of the appended claims.

We claim:

1. The method of treating a liquid petroleum product containing small quantities of free or loosely combined sulfur to inhibit the tendency of such product to deposit a copper sulfide stain on the surfaces of copper and copper alloys with 40 which such product comes into contact which comprises adding to said petroleum product in liquid phase a compound, substantially inert to said product, of the formula RON where R is a member of the class consisting of aliphatic and aromatic radicals.

2. The method of treating a mineral lubricating oil, containing additives of a sulfur-yielding nature, to inhibit the tendency of such oil to deposit a copper sulfide stain on the surfaces of copper and copper alloys with which such oil comes into contact which comprises adding to the said oil in liquid phase a compound, substantially inert to said sulfur-yielding additives, of the formula v I RCN where R is a member of the class consisting of aliphatic and aromatic radicals.

3. The method of inhibiting the tendency of a sulfur-containing lubricating oil additive to impart metal staining characteristics to a mineral lubricating oil, when such staining tendency is due to the presence of small amounts of sulfuryielding materials in the additive, which comprises treating said additive in liquid phase with a compound, substantially inert to said additive, ot the formula RCN where R is a member of the class consisting of aliphatic and aromatic radicals.

4. A method according to claim 3 in which RON is an alkyl nitrile having more than four solution of an alkali or alkaline earth cyanide, ll carbon atoms.

where R is a member of the class consisting of aliphatic and aromatic radicals.

7. The method according toclaim 7 in which RCN is an alkyl nitrile having a molecular weight above about 83.

8. A method according to claim 3 in'which new is. an alkyl-nitrile having 10 to 20 cal-son atoms.

9. The method of inhibiting the tendency of a. metallic salt oi an alkylated phenol disulfide to impart metal staining tendencies to a mineral oil containing the same, which comprises -treat-.

ing said salt with about 2% to about 10% of a compound of the formula RON where R is a member or the class consisting of aliphatic and aromatic radicals.

10. A method according to claim 9 in which RCN is an alkyl nitrile having more than three carbon atoms in the alkyl group.

Davin w. YOUNG.

monoaa J. mamas, .m. 

